Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Magnetotransport in the nonconventional pictures of magnetic levels in the two-dimensional p-Ge and HgTe

prof. Mikhail Yakunin

Institute of Metal Physics, Ekaterinburg, Russia

The picture of magnetic levels in a quasi-2D potential is a sensitive tool to characterize the heterostructure, while creating an untraditional scheme of levels facilitates the analysis of fundamentals in the physics of Quantum Hall Effect (QHE). Several aspects will be presented in the talk. First, the coincidence effects of spin sublevels under tilted magnetic fields, traditional and with its further development, will be reported in applications to the 2D hole gas in the high-perfection Ge structures [1] and to the HgTe-based systems with inverted and quasi-Dirac energy spectrum [2]. The value of the effective hole g-factor in Ge was found from these data with signs of its anisotropy. Then we report on the complicated system of the hole magnetic levels in the valence subband of HgTe and its manifestation in QHE. A new aspect here is the existence of lateral maxima in the valence subband that overlap with the conduction subband minimum resulting in a semimetal with coexisting 2D electrons and holes. We show that the value of the overlap may be enhanced and regulated by the gate voltage in the Double Quantum Well (DQW) created of two HgTe 2D layers separated by a thin CdHgTe barrier [3]. Unusual picture of the hole magnetic levels is displayed in the unconventional QHE with several inversion points in the Hall resistivity and in the existence of the zero-filling factor QH state. A DQW made of HgTe layers with thickness close to critical (6.5 nm) has an energy spectrum resembling that of a two-layer graphene. The picture of magnetic levels here consists of interfering electron-like and hole-like levels with multiple crossing points between them. We show that these points cause a QHE of an unusual structure with reentrant behavior between different QH states and with the signs of additional localization of holes in the valence subband lateral maxima.

[1]    O. A. Mironov et al., Phys. Rev. Lett. 116, 176802 (2016).
[2]    M.V. Yakunin et al., Phys. Rev. B 85, 245321 (2012).
[3]    M.V. Yakunin et al., Phys. Rev. B 93, 085308 (2016).